Respirator device particularly for use in perinatal medicine

ABSTRACT

A respirator device especially for the respiratory treatment of new-born and inmate infants and for their adaptation to natural breathing. The device comprises oxygen and air ducts, means for adjusting the composition, temperature, humidity, and other parameters of the gas mixture, a patient junction, and pressure adjusting valve means coupled to the junction shunting the gas flow in the junction in such a way that the gas pressure is positive both during expiration and inspiration. 
     The respiration demand of the patient is sensed by a means responsive to pressure drops which controls a starting signal generator and a beat generator. The beat generator controls the valve means. The device can be adjusted to controlled respiration, controlled assisted respiration, inspected and assisted respiration, and continuous positive airway pressure modes, whereby it can be adapted to various respiratory diseases. In the inspecting modes a respiration stoppage detector senses the spontaneous inspirations and in response to a stoppage exceeding a predetermined waiting period, performs controlled respiration for a given period of time and starts an alarm.

FIELD OF THE INVENTION

The invention relates to a respirator device intended both forcontrolled breathing of new-born and premature infants or of laboratoryanimals and for making the infants to adapt to natural breathing, whichdevice can be used in hospital wards as well as during transportation.The respirator comprises respective oxygen and air receiving ducts,means for adjusting the composition of the oxygen-air mixture, a conduitfor transporting the mixture, a patient junction coupled to the conduit,a respiratory beat generator and pressure adjusting valve meanscontrolled by the beat generator.

BACKGROUND ART

In the field of perinatal medicine there are a large number of diseasesin which controlled respiration is required due to the lack orinsufficiency of breathing. In a significant parts of cases requiringsuch respiration the problem is caused by some kinds of pulmonarymalfunction, however, certain other types of diseases (e.g. paralysis ofthe breathing center,) also require controlled respiration. Of therespiratory problems of new-born and premature infants the idiopathicaldistress syndrome has a high incidence and it forms a major factor inperinatal mortality.

The controlled respiration raises in perinatal medicine a number ofspecial demands which are different from normal respiratory practice.For that reason the miniaturization of conventional respiratory devicescannot solve the specific problems of perinatal respiratory diseases.Although there are already a number of respirator devices designedparticularly for use in perinatal medicine, everyday practice has shownthat they could not solve in general the problems in this particularfield and they proved to be useful in comparatively narrow fields ofindications only.

The handling of pneumatically controlled respirators designed forperinatal medicine is often inconvenient and such respirators cannot beused for the treatment of a number of respiratory problems. For example,one problem connected with such respirators lies in that the pressure ofthe expirated gas cannot be adjusted to the required values. Accordingto another problem in the expirating periods, pressures below theatmospheric value might take place i.e., the respiration with continuouspositive pressure and the respiration with alternating positive pressurecannot be implemented, although such kinds of respiration are consideredto be necessary for the respiratory treatment of new-born infants.

The above summarized problems are also connected with respiratorscontrolled electronically, because in such respirators the possibilityof adjusting the pressure of expirated gas below the atmospheric valueis also not excluded.

Apart from these main problems conventional respirators do not meet thecomplex requirements of perinatal respiration when their otherfacilities like handling capabilities, adjustability and the performancein various breathing modes are considered.

The practice in perinatal respiratorial therapy necessitates that themode of respiration should be brought in correspondence with the type ofthe actual respiratory problem. Those kinds of respirator devices arerequired which can provide for a controlled mechanical respiration withalternating positive pressure if the lack or insufficiency ofspontaneous breathing is detected. This can be effected by anatmospheric pressure at the ending phase of the expiration, or byadjusting a slight positive pressure at the end of the expiration. Inmany respiratory disturbances it is required that the spontaneouslybreathing new-born or inmate baby breathe from a continuously streamingoxygen-air mixture with positive pressure.

OBJECT OF THE INVENTION

The object of the invention is to provide a respirator device which canmeet the complex demands of perinatal respiration and which can becapable of providing respiration in a perinatal ward or, if it isrequired, during transportation. The respirator device should havevarious modes of operation that enable the therapy of respiratoryproblems of new-born and inmate infants of different gravity and originincluding the specific perinatal diseases like the idiopathicrespiratory distress syndrome. In addition, the device should be able tomake the baby leave off respiratory treatment under inspected breathing.

SUMMARY OF THE INVENTION

According to the invention a respirator device has been provided,especially for the respiratory treatment of new-born and inmate infantswhich comprises respective oxygen and air receiving ducts, means foradjusting the composition of the oxygen-air mixture, a conduit fortransporting the mixture, a patient junction coupled to the conduit, abeat generator for determining the rhythm of breathing, and pressureadjusting valve means controlled by the output of the beat generator, inwhich according to the invention the respirator comprises a respirationdemand detector with an input coupled to the patient junction andcapable of detecting the pressure drop caused by the air intake of thepatient during the expiration period of the device, a starting signalgenerator which in response to the detected pressure drop generates acorresponding starting pulse, a mode controller for adjusting theoperational mode according to the actual requirement of the treatment,the beat generator comprises a generator unit provided with respectivecontrol inputs for the selection of continuous, triggered andretriggered modes of signal generation, the mode controller is used tocouple the required one of these inputs to the output of the startingsignal generator, and the pressure adjusting valve means is coupled tothe patient junction and provides adjustable positive pressures both ininspiration and expiration at the junction by the controlled release ofthe oxygen-air mixture in the atmosphere.

In a preferable embodiment the output of the starting signal generatoris coupled to the input of a respiration stoppage detector for providingan appropriate signal when no output pulse is received from the startingsignal generation within a predetermined period of time, and this signalis coupled by the mode controller to the beat generator.

The respirator device according to the invention can be used in fourbasic modes of operation, i.e., controlled respiration for use in theabsence of spontaneous breathing; controlled assisted respirationintended for use in the occurrence of repeated spontaneous breathing;inspected and assisted respiration which can be used after the formationof sufficient spontaneous breathing; and the inspected continuouspositive airway pressure mode for use in respiratory therapy.

The invention is based on the particular way of watching the spontaneousinspiration of the patient and on the specific reaction generated inresponse thereto. The watching operation is carried out by therespiration demand detector, made preferably of a pressuredifference--capacitance converter utilizing a metal membrane, in which areference pressure is established in accordance with the preadjustedexpiration pressure.

The respirator device according to the invention is capable of providingthe new-born infant suffering from a respiratory disease with therequired amount of streaming ionized gas to its trachea, which gas isfresh, having adjustable composition, humidity and inspiration andexpiration pressure with controlled rate and duty cycle, and owing toits various adjustable modes of operation it provides a possibility formaking the patient leave off instrumental respiration in such a way thata smooth transition is provided towards the normal breathing in theatmospheric air.

DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the general block diagram of the respiratory apparatusaccording to the invention;

FIG. 2 shows the respiration demand detector in sectional elevationview;

FIG. 3 is a more detailed block diagram of the electrical units of therespiratory apparatus;

FIGS. 4 and 5 show signal condition curves measured in typical points ofthe starting signal generator;

FIG. 6 shows signal curves measured in typical points of the beatgenerator;

FIG. 7 shows the pressure versus time curves in all the four operationalmodes; and

FIG. 8 illustrates in diagrammatic form the restarting operation of thegenerator in controlled assisted mode.

DETAILED DESCRIPTION OF THE INVENTION

Reference is made now to FIG. 1 showing the general block diagram of therespirator according to the invention. Oxygen stored in a predeterminedoverpressure is lead to the respirator through oxygen receiving duct 1and pressurized air is coupled to the respirator through an airreceiving duct 2. The output of the oxygen receiving duct 1 is connectedthrough an oxygen filter 3, a pin valve 5, and a flow meter 7 to acommon conduit used for the transportation of oxygen-air mixture.Similarly, the air receiving duct 2 is connected to the same conduitthrough an air filter 4, a pin valve 6, and a flowmeter 8.

A safety valve 9 is coupled to the common conduit for preventing theestablishment of pressures above a predetermined maximum value. Thecommon conduit passes a gas-mixture heater 10, means 11 for adjustingthe relative humidity of the mixture, and an ionizer 12, by which themixture can be adjusted to a required temperature and humidity and itcan also be ionized. The temperature of the gas leaving the ionizer 12is sensed by a temperature detector 13 which generates an analogueelectrical temperature control signal coupled to the control input ofthe gas-mixture heater 10.

The conduit of the oxygen-air mixture is coupled through a connection 14to a patient junction 17 and the latter is formed substantially by aclosed little room communicating with four openings. The first openingis connected to the connection 14 for receiving the overpressurizedoxygen-air mixture. The second opening is connected to a secondconnection 15, through which it is coupled to a manometer 18 and to arespiration demand detector 19. The third opening is coupled through aconnection 16 to pressure adjusting valves 24. The oxygen-air mixture isreleased through the valves 24 to the free atmosphere underpredetermined pressure values. The pressure prevailing in the respiratoris determined by the condition of the valves 24. The fourth opening ofthe patient junction 17 is connected through a suitably designedflexible tube to the respiratory system of the new-born or of thepatient under treatment.

The respiration demand detector 19 is designed substantially as apressure-capacitance transducer, which is capable of converting thepressure changes occurring in the patient junction 17 relative to apredetermined reference pressure value into a capacitance change. Anexemplary embodiment of the respiration demand detector 19 will bedescribed in connection with FIG. 2.

The output of the respiration demand detector 19 is coupled to astarting signal generator 20 which senses the pressure drop caused bythe spontaneous intake of air by the new-born and generates a startingsignal. The output of the starting signal generator is coupled to a beatgenerator 21 and to a respiration stoppage detector 22. In certain modesof operation of the respirator the respiration stoppage detector 22senses if the spontaneous breathing of the new-born has stoppedthroughout a given period of time, and in such conditions it generates asignal for the beat generator 21 and for an alarming device 25.

The beat generator 21 is adapted to adjust the parameters of therespiratory cycles and a mode controller 26 is used for setting the modeof operation of the beat generator 21. The output of the beat generator21 is coupled through an amplifier 23 to the control input of thepressure adjusting valves 24 and provides for the appropriate control ofthe valves.

Now reference will be made to FIG. 2 in which the structural design of apreferable embodiment of the respiratory demand detector 19 is shown.The respiratory demand detector comprises a case 30 defining acylindrical inner room divided into two parts by a metal membrane 31.The upper part comprises a duct 32 connected to conduit 33 through whichthe inner room is coupled to a pressure adjusting assembly 34 adapted toset a required overpressure for reference purposes. A disc 35 isarranged in the case 30 spaced above the metal membrane 31 and isprovided with a plurality of perforations. At the other side of themetal membrane 31 opposite to the disc 35 another disc 36 is providedwhich also has perforations and on the surface of the disc 36 that facesthe membrane 31 an electrically conductive coating is provided. Themetal membrane 31 and the disc 36 together form a capacitor and the twoterminals thereof are coupled to the input of the starting signalgenerator 20 (FIG. 1). The lower space of the case 30 communicatesthrough a duct 37 with a flexible tube 38 which is coupled to themanometer 18 and to the connection 15 of the patient junction 17.

The pressure adjusting assembly 34 comprises a piston displaceable in acylindrical house and its axial displacement is adjusted by a threadedknob 39 by which the pressure acting on the upper side of the metalmembrane 31 can be set to the desired value. During operation of therespirator a slightly increased pressure compared to the atmospheric one(e.g. 0.4 to 0.5 kPa) is established in the respiratory system of thepatient even in the expiration phase, and the pressure adjustingassembly 34 is used to establish a reference pressure in the spacceabove the metal membrane 31 which is lower by about 0.05 kPa than therequired expiration pressure If the new born provides a pressure-drophigher than this 0.05 kPa value during inspiration in the interior ofthe patient junction 17, then the pressure below the metal membrane 31will be smaller than that prevailing above the membrane 31, and thepressure in the upper part established by the pressure adjustingassembly 34 displaces the metal membrane 31 towards the lower disc 36,whereby the capacitance of the above mentioned capacitor will beincreased.

New reference will be made to FIG. 3 in which the units used foradjusting the parameters of the respiration is shown in detail. The twoterminals of the pressure-sensing capacitor of the respiration demanddetector 19 are coupled to the inputs of an astable multivibrator 201that define the duty cycle thereof. Another astable multivibrator 202 isrunning together with the first astable multivibrator 201 which has thesame nominal frequency and fixed duty cycle. The two multivibrators aresynchronized in such a way that each of their periods is started at thesame moment. The outputs of the astable multivibrators 201 and 202 arecoupled to respective inputs of a logical gating circuit 203 formedexpediently by a half antivalence gate, and the output of the gatingcircuit 203 is coupled to an integrating circuit 204. The above circuitsform together the starting signal generator 20 shown in FIG. 1. Beforediscussing the other parts of the apparatus in detail the generation ofthe starting signal will be explained in connection with FIGS. 4 and 5.

The astable multivibrator 202 generates constant frequency pulses withperiods T₁ (FIG. 4a). The starting of the respective periods of theastable multivibrator 201 coincides with that of the multivibrator 202.It is supposed that before the moment t_(o) no inspiration takes placeand the width of the output pulses of the astable multivibrator 201 issmaller than that of the other multivibrator 202 (FIG. 4b). After themoment t_(o) inspiration takes place, whereby the capacitance of thecapacitor in the respiration demand detector 19 increases and thisincrease extends the width of the astable multivibrator 201. The astablemultivibrator 201 is adjusted in such a way that the width of its outputpulses reach the width of the pulses of the other multivibrator 202 whenthe pressure established by the inspiration of the new-born just equalsthe reference pressure set by the pressure adjusting assembly 34.

The logical 0 and 1 symbols shown in FIG. 4c illustrate the outputvariables at the outputs of the astable multivibrators 201 and 202 andof the logical gating circuit 203. The output of the gating circuit 203is on logic 1 level only if the output of the astable multivibrator 201is on 1 level and the output of the astable multivibrator 202 is on 0level. This condition can take place during inspiration only. FIG. 5aillustrates the signals at the input of the integrating circuit 204 andFIG. 5b shows the integrator output.

During the inspiration period of the newborn the gating circuit 203provides respective output pulses in each period of the astablemultivibrators 201 and 202, and the output signal of the integratingcircuit 204 increases in a stepwise manner due to the integration ofsuch output pulses. In FIGS. 4 and 5 an enlarged time scale is usedcompared to the respiration cycles, which means that the integratedpulse shown in FIG. 5b is very short compared to a respiratory cyclei.e., the integrator output produces practically immediately a pulse inresponse to the detection of the inspiration. The integration process isrequired for the elimination of random disturbances and for the sake ofneglecting the insufficient inspiration efforts. All sufficientinspiration of the new-born is associated with the generation of arespective pulse.

Reference is made again to FIG. 3 in which it is illustrated that theoutput of the integrating circuit 204 is coupled, on the first hand, tothe input of the respiration stoppage detector 22 (which can be, e.g.,retriggerable monostable multivibrator), and on the other hand, to theinput of a gating circuit 213. The gating circuit 213 comprises anotherinput receiving the output of the respiration stoppage detector 22 andfour other control inputs which, in accordance with the four operationalmodes, are coupled to the outputs of the mode controller 26. The gatingcircuit 213 has three output terminals driven in accordance with theselected mode of operation, and these output terminals are coupled torespective inputs of a sawtooth generator 211. The sawtooth generator211 comprises a trigger input 214, a retriggered input 215, an astableinput 216, and a frequency adjusting input 217. The frequency adjustinginput 217 is coupled to a potentiometer (not shown) for setting therespiration frequency.

The output of the sawtooth generator 211 is coupled to the signal inputof a comparator 212 which latter has a reference input 218 coupled to apotentiometer (not shown) adjusting the expiration-inspiration ratio.

The sawtooth generator 211, the comparator 212, and the gating circuit213 form together the beat generator 21 shown in FIG. 1.

FIG. 3 illustrates the pressure adjusting valves 24 consisting of anelectrically controlled expiration valve 242 and a pneumatic inspirationvalve 241. The valves 241 and 242 communicate with the free atmosphere,and the pressure threshold levels at which they let the gas mixture flowout to the free space can be adjusted within wide ranges by means ofrespective threshold adjustingg inputs 243 and 244.

When no control signal is generated by the amplifier 23, the path of theconduit coming from the connection 16 is open towards the expirationvalve 242 and the comparatively low pressure threshold set for theexpiration valve 242 determines the pressure prevailing in the system.This threshold level is typically 0.4 to 0.5 kPa higher than the normalatmospheric pressure. When a control signal is generated by theamplifier 23, the passage through the expiration valve 242 is cut offand the pressure in the system will be determined by the threshold levelset for the inspiration valve 241 which corresponds typically to anoverpressure or 1.5 to 2.5 kPa. The inspiration valve 241 is ineffectiveduring expiration because the expiration valve 242 with its lowerthreshold level prevents the increase of pressure above that value.

The operation of the respirator according to the invention will bedescribed in connection with the time diagrams shown in FIGS. 6 to 8.

It is true for all modes of operation that the respirator receivesthrough the oxygen receiving duct 1 and the air receiving duct 2 oxygenand air with predetermined pressure from respective sources not shown inthe drawing. The ratio of the oxygen and the air can be adjusted todesired values by the pin valves 5 and 6, and the rotational flowmeters7 and 8 indicate the extent of the instantaneous gas flow. Theadjustment of the temperature and the relative humidity of the gasmixture and the ionization of the same is carried out by the units shownin FIG. 1, whereby a sterilized gas mixture with predeterminedtemperature, humidity and composition will flow through the connection14 towards the patient junction 17.

The respirator according to the invention can be operated by the modecontroller 26 in four modes of operation.

The first mode is the controlled respiration which should be used in theabsence of spontaneous breathing. In this mode the pressure of thestreaming gas mixture is rhythmically changed between respectivepre-adjustable inspiration and expiration pressure values. The number ofbreathing cycles as well as the ratio of expiration to inspiration canalso be adjusted within wide ranges.

In this mode of operation the astable input 216 of the sawtoothgenerator 211 receives an enable signal, and the frequency of thesawtooth generator 211 can be set by an adjusting potentiometer notillustrated in FIG. 3, and the sawtooth generator 211 generates acontinuous train of sawtooth signals. FIG. 6a shows the output of thesawtooth generator 211 and the reference level R of the comparator 212.When the increasing sawtooth signal reaches the reference level R, thecomparator 212 is turned over (FIG. 6b) and the expiration period isstarted. The logical value 1 of the comparator output corresponds toinspiration and the logical value 0 corresponds to expiration. If thefrequency of the sawtooth signals is changed, the ratio of theexpiration period to the inspiration will not change. The moments t₁, t₂and t₃ respectively indicate boundaries of time sections in therespective associated periods, in which the ratio of theexpiration/inspiration sections is constant. Obviously, theexpiration-to-inspiration ratio can be changed freely within wide limitsby changing the reference level R, and the so-adjusted ratio isindependent from the frequency setting.

FIG. 7 shows the pressure versus time diagram for the controlledrespiration mode A, and it can be seen that the pressure is changedindependently from the breathing efforts of the new-born.

The second mode B is the controlled assisted respiration which isrecommended when repeated spontaneous breathing is experienced. In thismode a controlled respiration takes place (diagram B in FIG. 7) and therespiration demand detector 19 is used to sense the moments when thepatient begins breathing in. If such an inspiration is sensed (themoments of which being indicated by short vertical arrows in FIG. 7),the respirator is immediately switched over to inspiration, which meansthat the respirator is made to adapt itself to the breathing rhythm ofthe patient.

This process is illustrated in FIGS. 8a and 8b in detail. In thecontrolled assisted respiration position of the mode controller 26 theretriggered input 215 of the sawtooth generator 211 receives the enablesignal. In this mode the sawtooth generator 211 oscillates continuouslyjust as in the previous mode and the pressure in the system changesperiodically according to the present values. In this mode, however, ateach spontaneous inspiration a corresponding pulse is generated at theoutput of the integrating circuit 204. The gating circuit 213 passes thepulse associated with the spontaneous inspiration to the retriggeredinput 215 of the sawtooth generator 211, which in response to suchcontrol starts immediately a new sawtooth cycle. In FIG. 8a the shortvertical arrows indicate the inspiration moments, and it can be seenthat in response to such events a new cycle is started which alwaysbegins with an inspiration cycle. The demand of the patient forinspiration will therefore be immediately satisfied.

The third mode C of the respirator is the inspected and assistedrespiration. This mode is preferable when during the therapy asufficient spontaneous breathing is established. In this mode there isno controlled respiration with fixed frequency, and the rhythm ofrespiration is determined only by the inspiration demand of the patient.In diagram C of FIG. 7 the inspiration moments are illustrated by theshort vertical arrows. Each inspiration is sensed by the respirationdemand detector 19 and a corresponding starting pulse is generated bythe starting signal generator 20.

A mode controller 26 controls now the gating circuit 213 to send theenable signal to the trigger input 214 of the sawtooth generator 211 andto establish a path between the output of the respiration stoppagedetector 22 and the astable input 216 of the sawtooth generator 211.Sawtooth generation will take place only if the trigger input 214receives a control signal from the output of the integrating circuit204. This occurs always at the beginning of the spontaneous inspirationof the patient. In the starting period of the sawtooth generator 211 aninspiration begins which is followed by an expiration period which lastsuntil the next starting moment.

It can be seen in diagram C of FIG. 7 that each spontaneous inspirationis associated with the beginning of an inspiration period. The rhythm ofthe breathing is determined by the demand of the patient.

The inspecting function lies in that in every inspiration moment therespiration stoppage detector 22 starts a waiting period which is about15 seconds long. If the subsequent inspiration occurs within the waitingperiod, then a new waiting period is started and the condition of therespiration stoppage detector 22 will not change. If the waiting periodis finished and no inspiration occurs, it will change the logicalcondition of the respiration stoppage detector 22, and the astable input216 of the sawtooth generator will be activated and a controlledrespiration will take place according to the controlled respiration modefor a predetermined period of time. At the same time the respirationstoppage detector 22 controls the alarming device 25, whereby asufficient alarm will be generated.

In diagram C of FIG. 7 the period T₂ shows the waiting period thatcorresponds to the maximum stoppage of the breathing. This is followedby the controlled respiration for a period T₃. This period T₃ laststypically for 10 seconds and its value can be freely adjusted betweenappropriate limits. If a spontaneous breathing begins following thecontrolled respiration period, the assisted respiration will becontinued.

The fourth mode of operation D of the respiration is the inspectedcontinuous positive airway pressure CPAP. This mode D is very similar tothe CPAP mode commonly used in respiratory therapy, in which the patientspontaneously breathes from the streaming gas mixture with positivepressure.

The difference compared to the conventional CPAP mode lies in the way ofresponding to a stoppage of spontaneous breathing. Contrary to theconventional modes, the inspection is not performed by the nursingpersonnel, but automatically by the inspection function of therespirator.

The mode controller 26 establishes now a path through the gating circuit203 between the output of the respiration stoppage detector 22 and theastable input 216 of the sawtooth generator 211.

Owing to this constructional design, controlled respiration does nottake place until a respiration stoppage is sensed and the sawtoothgenerator 211 is not running either. The inspiration of the patient isinspected in the way described earlier and at the beginning of eachinspiration period the respiration stoppage detector 22 startsrespective waiting periods T₂. In diagram D of FIG. 7 the inspirationmoments are indicated by short vertical arrows. If no inspiration issensed during the predetermined waiting period T₂, the respirationstoppage detector 22 enables the alarming device 25 and controls thesawtooth generator 211 to start astable oscillation for a period T₃. Asa result of this control a controlled respiration will take place for aperiod of 10 seconds, whereafter the respirator returns to the CPAP modeand to the inspection of the respiration.

It can be seen from the above description of the respirator according tothe invention that besides its simple circuit design, it can be usedquickly and effectively in any kind of respiratory disturbances. Withthe above-described design the respirator cannot establish pressure lessthan the atmospheric value.

The construction of the respirator according to the invention can berealized in small sizes in portable casing and it can also be arrangedin an incubator. The application of such a respirator provides for thepossibility of gas sterilization when the respiration is in assembledcondition and it provides also for the appropriate setting of thecomposition, temperature and humidity of the gas mixture, for itsionization and for the adjustment of required respiratory parameters.

We claim:
 1. A respirator device, particularly for the respiratorytreatment of new-born and inmate infants, comprising an oxygen (1) andan air (2) duct coupled respectively to a source of oxygen andpressurized air, a mixing conduit for receiving said oxygen and air,valve means (5, 6) for adjusting the oxygen-air ratio of said mixture, aconduit coupled to said valve means conducting said mixture, a patientjunction (17) coupled to said conduit, a controlled beat generator (21)for determining the rhythm of breathing and having an output, a pressureadjusting valve means (24) controlled by the output of the beatgenerator (21) and coupled to the patient junction for providingadjustable positive pressure threshold levels both during theinspiration and expiration periods, a respiration demand detector (19)comprising an input and an output, said input of said demand detector iscoupled to the patient junction (17) for detecting the pressure dropcaused by the patient during inspiration, a starting signal generator(20) having an input connected to the output of the respiration demanddetector (19) for generating a starting signal in response to thedetected pressure drop of each detected inspiration, said startingsignal generator (20) comprising an output, said beat generator (21)comprises a sawtooth generator (211) having a trigger input (214), aretriggered input (215) and an astable input (216) and an output whereinsaid trigger input (214) is associated with assisted respiration; saidretriggered input (215) is associated with controlled assistedrespiration, and said astable input (216) is associated with controlledrespiration in absence of spontaneous breathing, a gating circuit (213)comprising three outputs each being coupled to a respective one of saidinputs (214, 215, 216) of said sawtooth generator, said gating circuit(213) comprising an input connected to the output of the starting signalgenerator (20), a respiration stoppage detector comprising an input andoutput, said output of the starting generator (20) is connected also tosaid respiration stoppage detector (22) for sensing the presence ofspontaneous breathing and for providing a signal in the absence of anoutput pulse from the starting signal generator (20) within apredetermined period of time, the gating circuit (213) comprises aplurality of enabling inputs, a mode controller (26) for the selectionof the operational mode corresponding to the required treatment andhaving a plurality of outputs connected to respective outputs of saidmode controller (26) and accordingly selecting an appropriate one of thetrigger, retrigger or astable inputs (214, 215, 216) of the sawtoothgenerator (211) in accordance with the setting of said mode controller(26) set by the operator, a comparator (212), said pressure adjustingvalve means (24) comprising a control input, said output of the sawtoothgenerator (211) is connected via said comparator (212) to said controlinput of said pressure adjusting valve means (24), wherein said demanddetector (19) is formed by a membrane-operated pressuredifference-to-capacitance transducer comprising a housing (30) dividedby a metal membrane (31) into two chambers, a pressure adjustingassembly (34) is coupled to one of said chambers, the other chambercommunicating with an interior of the patient junction (17), and whereinsaid pressure adjusting valve means (24) comprises a controlledexpiration valve (242) having a control input coupled to the output ofthe beat generator (21) and a pneumatic input coupled to the patientjunction (17) which in rest condition defining the expiration pressure,and an inspiration valve (241) having an input coupled to the patientjunction (17) and in the on condition of the expiration valve (242)defining the inspiration pressure.
 2. The respirator device as claimedin claim 1, wherein the respiration stoppage detector (22) is formed bya monostable multivibrator and having an input coupled to an alarmdevice (25) for generating a breathing stoppage alarm.
 3. A respiratordevice, particularly for the respiratory treatment of new-born andinmate infants, comprising an oxygen (1) and an air (2) duct coupledrespectively to a source of oxygen and pressurized air, a mixing conduitfor receiving said oxygen and air, valve means (5, 6) for adjusting theoxygen-air ratio of said mixture, a conduit coupled to said valve meansconducting said mixture, a patient junction (17) coupled to saidconduit, a controlled beat generator (21) for determining the rhythm ofbreathing and having an output, a pressure adjusting valve means (24)controlled by the output of the beat generator (21) and coupled to thepatient junction for providing adjustable positive pressure thresholdlevels both during the inspiration and expiration periods, a respirationdemand detector (19) comprising an input and an output, said input ofsaid demand detector is coupled to the patient junction (17) fordetecting the pressure drop caused by the patient during inspiration, astarting signal generator (20) having an input connected to the outputof the respiration demand detector (19) for generating a starting signalin response to the detected pressure drop of each detected inspiration,said starting signal generator (20) comprising an output, said beatgenerator (21) comprises a sawtooth generator (211) having a triggerinput (214), a retriggered input (215) and an astable input (216) and anoutput wherein said trigger input (214) is associated with assistedrespiration; said retriggered input (215) is associated with controlledassisted respiration, and said astable input (216) is associated withcontrolled respiration in absence of spontaneous breathing, a gatingcircuit (213) comprising three outputs each being coupled to arespective one of said inputs (214, 215, 216) of said sawtoothgenerator, said gating circuit (213) comprising an input connected tothe output of the starting signal generator (20), a respiration stoppagedetector comprising an input and output, said output of the startinggenerator (20) is connected also to said respiration stoppage detector(22) for sensing the presence of spontaneous breathing and for providinga signal in the absence of an output pulse from the starting signalgenerator (20) within a predetermined period of time, the gating circuit(213) comprises a plurality of enabling inputs, a mode controller (26)for the selection of the operational mode corresponding to the requiredtreatment and having a plurality of outputs connected to respectiveoutputs of said mode controller (26) and accordingly selecting anappropriate one of the trigger, retrigger or astable inputs (214, 215,216) of the sawtooth generator (211) in accordance with the setting ofsaid mode controller (26) set by the operator, a comparator (212), saidpressure adjusting valve means (24) comprising a control input, saidoutput of the sawtooth generator (211) is connected via said comparator(212) to said control input of said pressure adjusting valve means (24),wherein said respiration demand detector comprises a case divided intofirst and second chambers by a metal membrane, a pressure adjustingassembly, said first chamber communicating with said pressure adjustingassembly and said second chamber communicating with said patientjunction means, and further comprises a perforated disc located in saidsecond chamber and confronting said metal membrane, said perforated discbeing coated with electrically conductive material such that said metalmembrane and said perforated disc comprise a capacitor.
 4. A respiratoras in claim 3, wherein changes in pressure in said second chamberproduce corresponding changes in the capacitance of said capacitor, saidcapacitor being coupled to the input of said starting signal generator.5. A respirator device, particularly for the respiratory treatment ofnew-born and inmate infants, comprising an oxygen (1) and an air (2)duct coupled respectively to a source of oxygen and pressurized air, amixing conduit for receiving said oxygen and air, valve means (5, 6) foradjusting the oxygen-air ratio of said mixture, a conduit coupled tosaid valve means conducting said mixture, a patient junction (17)coupled to said conduit, a controlled beat generator (21) fordetermining the rhythm of breathing and having an output, a pressureadjusting valve means (24) controlled by the output of the beatgenerator (21) and coupled to the patient junction for providingadjustable positive pressure threshold levels both during theinspiration and expiration periods, a respiration demand detector (19)comprising an input and an output, said input of said demand detector iscoupled to the patient junction (17) for detecting the pressure dropcaused by the patient during inspiration, a starting signal generator(20) having an input connected to the output of the respiration demanddetector (19) for generating a starting signal in response to thedetected pressure drop of each detected inspiration, said startingsignal generator (20) comprising an output, said beat generator (21)comprises a sawtooth generator (211) having a trigger input (214), aretriggered input (215) and an astable input (216) and an output whereinsaid trigger input (214) is associated with assisted respiration; saidretriggered input (215) is associated with controlled assistedrespiration, and said astable input (216) is associated with controlledrespiration in absence of spontaneous breathing, a gating circuit (213)comprising three outputs each being coupled to a respective one of saidinputs (214, 215, 216) of said sawtooth generator, said gating circuit(213) comprising an input connected to the output of the starting signalgenerator (20), a respiration stoppage detector comprising an input andoutput, said output of the starting generator (20) is connected also tosaid respiration stoppage detector (22) for sensing the presence ofspontaneous breathing and for providing a signal in the absence of anoutput pulse from the starting signal generator (20) within apredetermined period of time, the gating circuit (213) comprises aplurality of enabling inputs, a mode controller (26) for the selectionof the operational mode corresponding to the required treatment andhaving a plurality of outputs connected to respective outputs of saidmode controller (26) and accordingly selecting an appropriate one of thetrigger, retrigger or astable inputs (214, 215, 216) of the sawtoothgenerator (211) in accordance with the setting of said mode controller(26) set by the operator, a comparator (212), said pressure adjustingvalve means (24) comprising a control input, said output of the sawtoothgenerator (211) is connected via said comparator (212) to said controlinput of said pressure adjusting valve means (24), wherein the startingsignal generator (20) comprises a pair of synchronously started astablemultivibrators (201, 202), the first astable multivibrator (201)comprises a control input for adjusting the duty cycle being coupled tothe output of the respiration demand detector (19), said generator (20)comprises additionally a gating circuit (203) having respective inputscoupled to the outputs of the astable multivibrators (201, 202), and anintegrating circuit (204) having an input coupled to the output of thegating circuit (203) and its output forming the output of the startingsignal generator (20).